Many therapeutic agents are most effective when made available at a constant rate at or near the absorption site. The absorption of therapeutic agents thus made available generally results in desired plasma concentrations leading to maximum efficacy and minimum toxic side effects. Much effort has been devoted to developing matrix tablet based and multi-particulate capsule based drug delivery systems for oral applications.
U.S. Pat. No. 4,839,177 to Colombo, et al, assigned to Jagotec AG, refers broadly to controlled release of active substances including medicaments and any type of substance which is to be released at a controlled rate into an aqueous fluid. The patent is directed to a system for the controlled-rate release of active substances consisting of a deposit core comprising an active substance and at least one of (a) a polymeric material having a high degree of swelling on contact with water and a gellable polymeric material or (b) a single polymeric material having both swelling and gelling properties, and a support platform applied to the deposit core wherein the support platform consists of a water insoluble polymeric material.
U.S. Pat. No. 4,851,228 and U.S. Pat. No. 4,968,507, both to Zentner et al., assigned to Merck & Company, refer to a multi-particulate osmotic pump for the controlled release of a pharmaceutically active agent, each osmotic pump element consisting essentially of a core containing an active agent and a rate controlling water insoluble wall comprising a semi-permeable polymer and at least one pH insensitive pore forming additive dispersed throughout the wall. U.S. Pat. No. 4,590,062 to Jang assigned to Tech Trade Corporation and U.S. Pat. No. 4,882,167 to Jang, are directed to a compressed product containing an active produced by dry blending with a matrix combination of a hydrophobic polymer (e.g. ethylcellulose) and a wax, fatty acid, neutral lipid or combination thereof.
U.S. Pat. No. 4,996,047 to Kelleher, assigned to Richardson-Vicks, is directed to an oral pharmaceutical composition in unit dosage form of ion-exchange resin particles having a pharmacologically active drug bound thereto wherein the drug-resin complex particles have been coated with a water-impermeable diffusion barrier to provide controlled release of the active drug. U.S. Pat. No. 5,120,548 to McClelland et al., assigned to Merck & Company, is directed to a controlled release drug delivery device comprising a composition of a polymer which swells upon exposure to an aqueous environment, a plurality of controlled release swelling modulators, at least one active agent and either a water insoluble polymer coating surrounding the composition or a microporous wall surrounding the composition. U.S. Pat. No. 5,350,584 to McClelland et al., assigned to Merck & Company, relates to a process for the production of microcrystalline cellulose-free multiparticulates comprising a medicament and a charged resin. The resulting spheronized beads can be used in certain controlled release dosage forms.
U.S. Pat. No. 5,366,738 to Rork et al., assigned to Merck & Company, is directed to a drug delivery device for controlled release of an active agent. The drug delivery device includes a compressed core with an active agent and a polymer which forms gelatinous microscopic particles upon hydration and a water insoluble, water impermeable polymeric coating comprising a polymer and plasticizer which surrounds and adheres to the core.
U.S. Pat. No. 5,582,838 to Rork et al., assigned to Merck & Company, is related to a drug delivery device for the controlled release of a beneficial agent. The drug delivery device includes a compressed core having at least two layers: at least one layer is a mixture of a beneficial agent and a polymer which forms microscopic polymer gel beads upon hydration and at least one outer layer comprises a polymer which forms microscopic polymer gel beads upon hydration. A water insoluble, water impermeable coating is applied to the core and the coating has apertures exposing between about 5-75% of the core surface.
U.S. Pat. No. 5,874,418 to Stella et al., assigned to Cydex, is directed to a pharmaceutical composition comprising a carrier and a mixture of a sulfoalkyl ether-cyclodextrin and a therapeutic agent wherein a major portion of the therapeutic agent is not complexed to the sulfoalkyl ether-cyclodextrin derivative. Delayed, sustained or controlled release formulations are also described wherein the pharmaceutical core is coated with a film coating comprising a file forming agent and a pore forming agent. U.S. Pat. No. 5,882,682 to Rork et al., assigned to Merck & Company, is directed to a drug delivery process including the steps of preparing a uniform mixture of a polymer which forms gelatinous microscopic particles upon hydration, the beneficial agent and other excipients used in the preparation of the core; compressing the mixture into cores; coating the entire core with a water insoluble, water impermeable polymeric coating including a polymer and a plasticizer; and forming apertures through the coating.
U.S. Pat. No. 5,952,451 to Zhao, assigned to Guilford Pharmaceuticals is directed to a process for preparing high molecular weight polyphosphoester) compositions comprising a biologically active substance and a poly(phosphoester) and the high molecular weight compositions produced thereby. The polymers so produced are useful in prolonged released drug delivery systems. U.S. Pat. No. 6,004,582 to Faour et al., assigned to Laboratorios Phoenix U.S.A., is directed to a multi-layered osmotic device comprising a compressed core including a first active agent and an osmotic agent, a semi-permeable membrane surrounding the core and having a preformed passageway therein wherein the membrane is permeable to a fluid in the environment of use and substantially impermeable to the first active agent. The semi-permeable membrane preferably consists essentially of cellulose acetate and poly(ethylene glycol). The external coat can includes poly(vinylpyrrolidone) and poly (ethylene glycol) and can further includes materials such as HPMC, ethylcellulose, hydroxylethylcellulose, CMC, dimethylaminoethyl methacrylate-methacrylic acid ester copolymer, ethyl acrylate-methyl methacrylate copolymer, and combinations thereof.
WO 99/18937 to Kleinbart et al., (Merck & Company), is directed to a composition comprising a pharmaceutically effective amount of cyclobenzaprine and calcium phosphate dibasic hydrous, wherein the tablet releases most of the active component within an hour. WO 99/30671 to Ron, is directed to an oral delivery vehicle including an aspected particle comprising a pharmaceutically active component and excipients wherein the vehicle is formulated to provide controlled delivery of the pharmaceutically active component. The vehicle may further contain a coating to provide sustained drug delivery to the particle. WO 98/53802 to Faour et al., Laboratorios Phoenix USA), is directed to a multi-layered osmotic device that is capable of delivering a first active agent in an outer lamina to one environment of use and a second active agent in the core to another environment of use. An erodible polymer coat between an internal semipermeable membrane and a second active agent-containing external coat comprises poly(vinylpyrrolidone)-vinyl acetate) copolymer. The active agent in the core is delivered through a pore containing an erodible plug.
WO 98/18610 to Van Lengerich, is directed to particles containing an active agent, which provide controlled release of the active ingredient without substantial destruction of the matrix material. A release-rate controlling component is incorporated in a matrix to control the rate-release of the encapsulant from the particles. A hydrophobic component or a high water binding capacity component may be used for extending the release time. Release properties may also be controlled by precoating the encapsulant and/or coating the particles with a film-forming component. WO 98/06439 to Oedemoed, (Osteotech), is directed to a composition comprising a biologically active agent encapsulated in a matrix comprising a polyether ester copolymer, such as polyethylene glycol terephthalate/polybutylene-terephthalate copolymer. The polyether ester copolymer protects the active agent from degradation and thereby facilitates the drug delivery.
Cyclobenzaprine hydrochloride, a skeletal muscle relaxant, is a centrally acting drug which reduces or abolishes excessive tonic muscle activity in hypertonic as opposed to hyperphasic disorders. Flexeril IR (immediate release) tablets containing 10 mg of cyclobenzaprine HCl are administered three times a day to relieve skeletal muscle spasm of local origin without interfering with muscle function. The oral administration thrice daily is an issue of patient compliance, especially with the elderly. Hence, there is a need for modified release skeletal muscle relaxant suitable for a single administration. More particularly, there is a need for modified release (MR) cyclobenzaprine hydrochloride capsules, 15 and 30 mg, which would substantially minimize intersubject variability and improve the quality of life, especially in the elderly population.